In 2021, I went through a phase of trying a variety of themes in Vim and Emacs: manual tweaks to the default themes, popular themes like Solarized and Gruvbox, even a theme with almost no colours at all. Gradually, my preferences shifted towards high-contrast light themes, such as PaperColor, due to their high legibility, even on dim screens. Then, on the 6th of August 2021 (or at least some time between then and the previous commit in my dotfiles repo), I tried Protesilaos Stavrou’s Modus Operandi, and was hooked.
Unlike most high-contrast themes I’ve used, Modus Operandi’s colours are well-balanced, avoiding things like the bright, harsh highlights of Emacs’ default theme, which put so many people off light themes in the first place. I am not aware of any theme for any other editor that pulls off the maximum-contrast of #000000 black on #ffffff white without becoming searingly unpleasant to look at.
It also strikes a nice balance between having its own identity and following modern conventions. Comments are grey, with errors and warnings highlighted in the typical red and yellow, while keywords use a shade of purple that I consider the most iconic feature of the theme.
On a more technical note, considering the Modus Themes project itself: when I first used them in 2021, they were some of the few themes that supported Neovim’s tree-sitter syntax highlighting capabilities. The Emacs versions of the themes specifically also offer improvements that should be available as a baseline, such as modus-themes-mixed-fonts, which allows certain elements like Org-mode tables to always render in a monospaced font, even if the main text of the buffer is variable-width.
The funny thing is, despite fact that that were originally Emacs themes, I was using Modus in Vim for about half a year before I discovered the original Emacs package. From then on, Modus Operandi has been the only theme I use in Emacs, except for the occasional switch to Modus Vivendi (its dark counterpart) if my eyes get especially tired. In short, these themes are amazing; thanks Prot! I recommend any Emacs user to try them out. If pure black/white seems too extreme, you could try modus-vivendi-tinted, which is a more typical dark theme.